syzbot


WARNING in u32_change

Status: upstream: reported C repro on 2026/02/22 20:25
Bug presence: origin:upstream
[Documentation on labels]
Reported-by: syzbot+b98f25656b791725fc13@syzkaller.appspotmail.com
First crash: 8d15h, last: 6d18h
Bug presence (1)
Date Name Commit Repro Result
2026/02/23 upstream (ToT) 6de23f81a5e0 C [report] WARNING in u32_change
Similar bugs (2)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream WARNING in u32_change net -1 C 28 1157d 1255d 22/29 fixed on 2023/02/24 13:50
linux-6.1 WARNING in u32_change -1 C 15 6d18h 8d16h 0/3 upstream: reported C repro on 2026/02/22 19:31

Sample crash report:
netlink: 44 bytes leftover after parsing attributes in process `syz.0.17'.
------------[ cut here ]------------
memcpy: detected field-spanning write (size 32) of single field "&new->sel" at net/sched/cls_u32.c:855 (size 16)
WARNING: CPU: 1 PID: 5919 at net/sched/cls_u32.c:855 u32_init_knode net/sched/cls_u32.c:855 [inline]
WARNING: CPU: 1 PID: 5919 at net/sched/cls_u32.c:855 u32_change+0x1c5a/0x24f0 net/sched/cls_u32.c:921
Modules linked in:
CPU: 1 PID: 5919 Comm: syz.0.17 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
RIP: 0010:u32_init_knode net/sched/cls_u32.c:855 [inline]
RIP: 0010:u32_change+0x1c5a/0x24f0 net/sched/cls_u32.c:921
Code: f8 eb 59 e8 a8 a0 d9 f8 c6 05 51 12 c8 05 01 b9 10 00 00 00 48 c7 c7 e0 40 c7 8b 4c 89 f6 48 c7 c2 60 41 c7 8b e8 16 62 a3 f8 <0f> 0b e9 86 f0 ff ff e8 7a a0 d9 f8 eb 24 e8 73 a0 d9 f8 c6 05 f3
RSP: 0018:ffffc90003336d40 EFLAGS: 00010246
RAX: ace4b4ca42a3a500 RBX: ffff888075abd800 RCX: ffff888024f33c00
RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000002
RBP: ffffc90003336ef8 R08: ffffc90003336947 R09: 1ffff92000666d28
R10: dffffc0000000000 R11: fffff52000666d29 R12: ffff888075abdc00
R13: ffff888075abdce8 R14: 0000000000000020 R15: ffff88801f761d40
FS:  000055557c829500(0000) GS:ffff8880b8f00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000200000006040 CR3: 0000000075864000 CR4: 00000000003506e0
Call Trace:
 <TASK>
 tc_new_tfilter+0xe4f/0x1640 net/sched/cls_api.c:2347
 rtnetlink_rcv_msg+0x8b8/0xfa0 net/core/rtnetlink.c:6463
 netlink_rcv_skb+0x241/0x4d0 net/netlink/af_netlink.c:2545
 netlink_unicast_kernel net/netlink/af_netlink.c:1320 [inline]
 netlink_unicast+0x751/0x8d0 net/netlink/af_netlink.c:1346
 netlink_sendmsg+0x8d0/0xbf0 net/netlink/af_netlink.c:1894
 sock_sendmsg_nosec net/socket.c:730 [inline]
 __sock_sendmsg net/socket.c:745 [inline]
 ____sys_sendmsg+0x5ba/0x960 net/socket.c:2594
 ___sys_sendmsg+0x2a6/0x360 net/socket.c:2648
 __sys_sendmmsg+0x2ca/0x510 net/socket.c:2734
 __do_sys_sendmmsg net/socket.c:2763 [inline]
 __se_sys_sendmmsg net/socket.c:2760 [inline]
 __x64_sys_sendmmsg+0xa0/0xb0 net/socket.c:2760
 do_syscall_x64 arch/x86/entry/common.c:46 [inline]
 do_syscall_64+0x55/0xa0 arch/x86/entry/common.c:76
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7fa9f279c629
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffc222a7f18 EFLAGS: 00000246 ORIG_RAX: 0000000000000133
RAX: ffffffffffffffda RBX: 00007fa9f2a15fa0 RCX: 00007fa9f279c629
RDX: 04000000000001f2 RSI: 0000200000000000 RDI: 0000000000000004
RBP: 00007fa9f2832b39 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fa9f2a15fac R14: 00007fa9f2a15fa0 R15: 00007fa9f2a15fa0
 </TASK>

Crashes (14):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/02/23 03:40 linux-6.6.y 7a137e9bfa0e 6e7b5511 .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan WARNING in u32_change
2026/02/23 02:21 linux-6.6.y 7a137e9bfa0e 6e7b5511 .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan WARNING in u32_change
2026/02/23 00:51 linux-6.6.y 7a137e9bfa0e 6e7b5511 .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan WARNING in u32_change
2026/02/22 23:30 linux-6.6.y 7a137e9bfa0e 6e7b5511 .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan WARNING in u32_change
2026/02/22 21:57 linux-6.6.y 7a137e9bfa0e 6e7b5511 .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan WARNING in u32_change
2026/02/24 17:56 linux-6.6.y 7a137e9bfa0e 96b1aa46 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan WARNING in u32_change
2026/02/24 17:55 linux-6.6.y 7a137e9bfa0e 96b1aa46 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan WARNING in u32_change
2026/02/24 09:02 linux-6.6.y 7a137e9bfa0e 41d2fa6a .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan WARNING in u32_change
2026/02/24 07:13 linux-6.6.y 7a137e9bfa0e 41d2fa6a .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan WARNING in u32_change
2026/02/24 06:26 linux-6.6.y 7a137e9bfa0e 41d2fa6a .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan WARNING in u32_change
2026/02/24 06:26 linux-6.6.y 7a137e9bfa0e 41d2fa6a .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan WARNING in u32_change
2026/02/24 05:50 linux-6.6.y 7a137e9bfa0e 41d2fa6a .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan WARNING in u32_change
2026/02/22 20:24 linux-6.6.y 7a137e9bfa0e 6e7b5511 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan WARNING in u32_change
2026/02/22 20:24 linux-6.6.y 7a137e9bfa0e 6e7b5511 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan WARNING in u32_change
* Struck through repros no longer work on HEAD.